An experimental and analytical investigation of the formation of a microporous layer of mixed ferricoxide and ferric hydroxide on a high-chromium alloy in alkaline solution under the oxygen evolutionregion is presented. By potentiostatic polarization under 5 VAg/AgCl, a dark red microporous layer wasformed on the surface of the high-chromium alloy. The workpieces and electrolytes were examined andanalyzed by scanning electron microscopy (SEM), X-ray fluorescence (XRF), Raman microscopy (RMS)and inductively coupled plasma (ICP) to probe the electrochemical mechanism of layer formation. Theresults demonstrate that under the set conditions, Fe(Ⅵ) ions were generated from the anode. However,due to the consumption of OHions, Fe(Ⅵ) ions were decomposed into ferric hydroxide; in turn, ferrichydroxide had an autocatalytic effect on the decomposition of Fe(Ⅵ) ions. The anodic reaction stepswere controlled by the mass transfer of OHions, and alternative transformation between Fe(Ⅵ) ionsand ferric hydroxide accelerated the formation of a microporous layer.
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